1. Field of the Invention
The present invention is directed to a support-request processing system using GPS data for locating a person requesting a support, and more particularly to such a system using a decentralized Global Positioning System (GPS) to locate a person requesting the support.
2. Description of the Prior Art
A decentralized GPS system such as disclosed in U.S. Pat. Nos. 5,119,102 and 5,379,224 has been proposed to reduce search of a person requesting an urgent support for rescue. The system utilizes a GPS terminal to be carried by a person, and a message center which is linked through a radio communication network to the GPS terminal and acts in response to a support-request signal from the person to give a warning message including a position of the person for prompting a suitable support. The GPS terminal is capable of acquiring GPS data from GPS satellites and of transmitting the support-request signal together with the GPS data to the message center. The GPS data is processed at the message center rather than at the GPS terminal for calculating a position of the mobile terminal so as to eliminate a calculation circuitry from the GPS terminal for reducing the cost of the GPS terminal. Thus decentralized GPS system, however, is still insufficient in that when the person is in a dead-area such as a building where the GPS data from the GPS satellites is not available but the radio communication with the message center is available, the support-request signal cannot be accompanied with a valid GPS data so that the message center fails to determine the position of the person, making it difficult to rescue the person.
In view of the above insufficiency, the present invention has been achieved to provide a system which is capable of estimating the position of the person even when the person issues the support-request signal after moving into a place, for example, a building where the GPS data is not available. The system of the present invention includes a mobile terminal having an identification (ID) code and being adapted to be carried by a person, and a message center linked to the mobile terminal over a radio communication network. The mobile terminal is composed of a GPS receiver capable of acquiring the GPS data from GPS satellites, a radio transmitter capable of transmitting the GPS data to the radio communication network, and a request key which issues the support-request signal. The support-request signal activates the GPS receiver to acquire current GPS data and activates the radio transmitter to transmit the current GPS data together with the support-request signal and the ID code to the message center. The message center has a database table storing a relation between the ID code and personal information about the person carrying the mobile terminal. Upon receiving the support-request signal accompanied with the GPS data and the ID code, the message center calculates the position of the mobile terminal and relates the calculated position to the personal information about the person with reference to the table. Then, the message center gives a support-request message including the calculated position and the related personal information for prompting a suitable support action. The characterizing feature of the present invention resides in that the mobile terminal is supplemented with a fail-safe recording means which acts independently of the support-request signal to acquire the GPS data from the GPS satellites at different times in accordance with a predetermined time schedule and stores plural time-series sets of thus acquired GPS data, and that the fail-safe recording means is linked to the radio transmitter so that the time-series sets of the GPS data are transmitted together with the current GPS data to the message center in response to the support-request signal. Therefore, even if the person moves into a building where the GPS satellites can not be reached but the mobile terminal can communicate with the message center, i.e., only an invalid GPS data is available, the message center can rely on the latest valid GPS data in the time-series sets to calculate the position of the person, giving a reliable estimation for locating the person.
In a preferred embodiment, the mobile terminal includes a start key which activates the fail-safe recording means to store the time-series sets of the GPS data.
The system may include a charger which is coupled to the mobile terminal to charge a rechargeable battery incorporated in the mobile terminal. In this case, the fail-safe recording means may be activated when the mobile terminal is disconnected from the charger. For this purpose, the mobile terminal has a charger detector which detects the disconnection of the mobile terminal from the charger and provides a start signal upon detection of the disconnection. In response to the start signal, the fail-safe recording means is activated to accumulate the time-series sets of the GPS data.
Also, the mobile terminal may be configured so that the radio terminal is capable of receiving a start signal from the message center through the radio communication network, which start signal activates the fail-safe recording means to accumulate the time-series sets of the GPS data.
Further, the mobile terminal may be programmed to transmit the time-series sets of the GPS data to the message center set by set to give one set of the GPS data at one time in descending time sequence. On the side of the message center, there is provided a check means which checks as to whether the current GPS data and those in the time-series sets is valid for calculation of the position of the mobile terminal. As soon as the GPS data is found to be valid, the check means transmits a stop signal to the mobile terminal, causing the mobile terminal to stop transmitting the remaining sets of the GPS data. Thus, it is possible to eliminate redundant procedures for prompt determination of the latest position of the mobile terminal.
In order to get a more comprehensive behavior of the person after requesting the support, the message center may transmits a follow-up request signal to the mobile terminal after a predetermined time from a first catch of calculating the position of the mobile terminal in reply to the support-request signal. In response to the follow-up request signal, the mobile terminal acts to acquire a fresh GPS data and transmit the fresh GPS data to the message center for updating the position of the mobile terminal, i.e., the person. Therefore, it is possible to update the latest position of the person still moving after requesting the support, assuring a reliable search for the person.
In addition to or instead of the above function of issuing the follow-up request signal from the message center to the mobile terminal, the mobile terminal itself may include a follow-up means which makes a process of acquiring a fresh GPS data from the GPS satellite and transmitting the same to the message center periodically at a predetermined time interval after the mobile terminal transmits the GPS data in response to the support-request signal.
Additionally, the system may include a monitoring capability of logging the position of the person when the person is going out of an effective radio communication area with the message center such that the person can be located at the last position if it is required to search the person for any reason other than by the person""s request. For this purpose, the mobile terminal may include a fade-out detecting means which detects whether the mobile terminal is moving closer to a border of the effective communication area based upon a received field intensity of a radio signal transmitted from a base station of the network, and generates a fade-out warning signal when the mobile terminal approaches to the border of the communication area. In response to the fade-out warning signal, the mobile terminal acquires a border GPS data indicative of the location near the border of the communication area and transmits the border GPS data as well as the fade-out warning signal together with the ID code to the message center. With this result, the message center can acknowledge the position of the person near the border of the communication area in relation to the personal information. The message center includes a storing means which, in response to the fade-out warning signal, stores the calculated position based upon the border GPS data with a tag indicating the presence of the fade-out warning signal. Therefore, when a search of the person is necessitated for any reason after the person moves out of the effective communication area, it is readily possible to retrieve the last position of the person near the border of the communication area, thereby facilitating to search for the missing person.
In this connection, the fade-out detecting means may be programmed to detect whether the mobile terminal is moving closer to the border of the communication area each time the mobile terminal receives the radio signal from the base station. Alternatively, the fade-out detecting means may be programmed to analyze the received field intensities of the radio signals consecutively received at the mobile terminal for the detection.
Further, the mobile terminal may have a revoke means which prohibits the radio transmitter from transmitting a further border GPS data in response to a further fade-out warning signal until an elapse of a predetermined time after the border GPS data is transmitted in response to the previous fade-out warning signal. Whereby, redundant operations of obtaining the duplicate positions of the person near the border of the communication area can be avoided.
In addition to or instead of the above capability of locating the person near the border of the effective communication area, the system may have a capability of recognizing the position of the person reentering the communication area. For this purpose, the mobile terminal is supplemented with a fade-in detecting means which detects whether the mobile terminal reenters the effective communication area based upon the received field intensity of the radio signal transmitted from the base station of the network, and generates a fade-in notice signal when the mobile terminal reenters the area. In response to the fade-in notice signal, the mobile terminal operates to acquire a border GPS data indicative of the position near the border of the area, and transmit the border GPS data as well as the fade-in notice signal together with the ID code to the message center. In this consequence, the message center can acknowledge the position of the person near the border of the communication area in relation to the personal information. Thus obtained position of the person is stored in the message center together with a tag indicating that the person reenters the area such that the person reentering the area can be immediately located. This is particularly advantageous in a situation where a search request by another person is accepted at the message center while the person is out of the communication area.
The fade-in detecting means may be programmed to determine whether the mobile terminal reenters the communication area each time the mobile terminal receives the radio signal from the base station, i.e., the person reenters the area. Alternatively, the fade-in detecting means may be programmed to analyze the received field intensities of the radio signals consecutively received at the mobile terminal for detection of the reentrance of the person.
In order to avoid redundant operations of obtaining the duplicate positions of the person near the border of the communication area, the mobile terminal may include a revoke means which prohibits from transmitting a further border GPS data in response to a further fade-in notice signal until an elapse of a predetermined time after the border GPS data is transmitted in response to the previous fade-in notice signal.
These and still other advantageous features of the present invention will become more apparent from the following detailed description of a preferred embodiment when taken in conjunction with the attached drawings.